1. Field of the Invention
The present invention is directed to a differential axle assembly and more particularly to such an assembly having a mechanism to selectively increase or decrease the speed of an output axle shaft using a planetary gear set.
2. Description of the Related Art
In a rear differential apparatus of a rear wheel drive or four wheel drive vehicle in accordance with the above related art, a driving force from an engine is input to a ring gear fixed to a differential case via a drive pinion. Right and left side gears of a bevel gear differential mechanism are respectively connected to right and left output shafts, an input gear of a control mechanism is connected to the differential case and the input gear is meshed with a first pinion gear. The first pinion gear is integrally formed with adjacent second and third pinion gears, which are respectively meshed with a first and second sun gears. The first sun gear at a speed increasing end and the second sun gear at a speed reducing end are respectively input to torque capacity variable couplings and are transmitted to a right output shaft via the respective couplings integrally formed. Friction torque due to an operation of the coupling is reversely transmitted to the differential case through the first sun gear, the second pinion gear, the first pinion gear and the input gear, or via the second sun gear, the third pinion gear, the first pinion gear and the input gear. Thus the distribution of the driving force between the right and left output shafts is controlled by the fact that any one of the increased or reduced couplings becomes in a driving force transmitting state.
In a front differential apparatus of a front wheel drive or four wheel drive vehicle for controlling a distribution of a driving force between right and left output shafts, a similar arrangement is provides as described above. In the front differential apparatus, a driving force from an engine is input to a ring gear of a planetary gear front differential apparatus of a double pinion meshed with an input gear. Then the driving force is output to a right output shaft via two rows of pinion gears meshed with a second gear fixed to a left output shaft, a first sun gear and a pinion carrier.
The second sun gear and a ring gear of a planetary gear mechanism of a double pinion disposed leftward are fixed to the left output shaft connected to a sun gear of a differential mechanism. A speed reducing clutch for directly reducing a rotational speed of a carrier member is disposed in the carrier member supporting the pinion gear meshed with the second sun gear, and a speed increasing clutch for increasing speed through the planetary gear mechanism is disposed.
However, there is a problem that a axial space becomes large since the former rear differential apparatus is provided with three rows of pinion gears in the control mechanism and the latter front differential apparatus is provided with three rows of gears comprising the first and second sun gears and the planetary gear mechanism.